Approximately 200 million people worldwide are chronically infected with HCV. This pathogen is the major cause of acute hepatitis and chronic liver disease, including cirrhosis and liver cancer and thereby HCV is the leading indication for liver transplantation [1]. HCV is an enveloped, positive-stranded RNA virus, member of the Flaviviridae family in the hepacivirus genus. HCV is closely related to the flavivirus genus, which includes a number of viruses implicated in human disease, such as dengue virus and yellow fever virus [2]. Seven major HCV genotypes and numerous subtypes have been described, which differ as much as ˜30% in the nucleotide sequences [3, 4]. The single stranded 9.6 kb genome consists of a single open reading frame (ORF) which is flanked at the 5′ and 3′ ends by highly structured and conserved non-translated regions (NTRs) important for both viral translation and viral replication [5]. At the 5′ end, the approximately 340 nucleotide long NTR sequence contains an internal ribosome entry site (IRES) that directs translation independent of a capstructure. The viral polyprotein is co- and posttranslationally processed into ten viral proteins (core, E1, E2, p7, NS2, NS3, NS4A, NS4B, NS5A, and NS5B). The HCV 5′NTR and its IRES are characterized by the formation of complexes with the host cell small ribosomal subunit (40 S) and eukaryotic initiation factor (eIF), resulting in the recognition of the viral start codon, thus starting the viral protein synthesis [6].
With the development of various cell culture models to study HCV, major progress has been made. Recently, it has become feasible to investigate all steps of the viral life cycle, entry, viral RNA replication, infectious viral particle formation (packaging, assembly and release) and in vivo infection using pseudoparticles (HCVpp) [11], subgenomic replicon cells [12], infectious cell culture system (HCVcc) [13] and transgenic mice [14], respectively. Among these, the development of the subgenomic replicon system was the most important advance, in that for the first time it was possible to utilize a cell-based assay to evaluate potential antiviral therapies. HCV subgenomic replicons consist of a HCV RNA in which the HCV structural region is replaced by the neomycin phosphotransferase gene and translation of the viral proteins NS3 to NS5 is directed by the encephalomyocarditis virus (EMCV) IRES element flanked by the 5′ and 3′ NTRs. Stable HCV RNA replication has been established in various liver and non-liver, human and non-human cell lines which are excellent tools to study the HCV life cycle and to validate novel antivirals [12, 15-17].
Despite increasing efforts to develop novel drugs effective against HCV, patients are being mainly treated with a virus-unspecific combination therapy of pegylated interferon alpha (PEG-IFN) and ribavirin (RBV). This treatment is expensive, associated with severe side effects and is effective in only 50-60% of patients infected with HCV genotype 1 [18]. Since early 2011, two direct acting antivirals (DAAs) targeting the viral NS3 protease are FDA approved. Unfortunately both drugs induce severe side effects, have a low resistance barrier and the administration regime is inconvenient to patients [19]. Furthermore, at one point, viral resistance may become an issue, and due to potential HCV genotype specificity, it is unclear whether all seven HCV genotypes and their subtypes are covered [20]. Therefore, it is a primary goal to identify targets with a significant higher genetic barrier of resistance covering all HCV genotypes. Other challenges include the appearance of escape mutants, the high costs of current therapy regimens, and their side effects. The mechanisms of resistance to IFN-based therapy through immune-system interception [21], and to DAAs like telaprevir and boceprevir through resistance conferring mutations could be avoided by combinatorial treatment. Although drugs targeting the virus are in clinical trials, there is a medical need for new HCV therapeutic agents. In particular, there is a need for HCV therapeutic agents that have broad activity against the majority of HCV genotypes and their subtypes (e.g. 1a/b, 2a/b, 3a/b, 4a/b, etc.). There is also a particular need for agents that are less susceptible to viral drug resistance.
Formula I compounds and Formula II compounds in accordance with the present invention, have been found to possess useful activity against all major HCV genotypes. Additionally, compounds in accordance with the present invention have been shown to have significant antiviral activity against drug resistant viruses (protease, NS5A and polymerase).
Drug combination experiments with compounds according to the present invention and selected HCV-specific FDA- and not yet FDA approved DAAs revealed beneficial properties that make them well suited to fulfill the current needs for HCV agents.
It was an object of the present invention to identify compounds with an anti-viral activity.
It was also an object of the present invention to identify compounds effective against viral disease, in particular HCV.